Speaker
Description
The inflationary universe predicts vacuum fluctuations of space-time, called primordial gravitational waves, whose spectra have slightly red-tilted and parity-symmetric features. This is an ordinary picture. Intriguingly, however, it is known that the axion-gauge coupling, motivated by string theory, could occur the particle production of gauge fields during inflation and provide the parity-violated blue tensor spectrum testable in future gravitational wave experiments, while no such a parity-violated primordial signal has been detected through recent observations. It seems that there would be no parity-violated phenomena in the early universe. In this talk, however, we suggests the new mechanism of providing blue tensor spectra sourced by gauge fields coupled to axions, surprisingly whose amplitudes are almost parity-conserved but slightly parity-violated! We expect that the blue tensor spectra with little chirality becomes the new window to the axion phenomenology in the early universe.
